Hello everyone, I am doing some evaluation on my 6 nodes mini cluster. Each node has 4 core Intel(R) Xeon(R) CPU 5130 @ 2.00GHz, 8GB memory, 500 GB disk, running Linux version 2.6.18-164.11.1.el5(Red Hat 4.1.2-46).
I was trying to use different packet size (dfs.write.packet.size) and bytePerChunksum(bpc) (io.bytes.per.checksum), with default block size and buffer size, to see how they impact the performance of creating a 1GB file. The default packet size is 64K, and, surprisingly, if I increase this value to 256K, 1M, etc, the performance drops gradually. Below is some result I got: time(ms): 25742 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 1024 packet size: 1048576 time(ms): 24960 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 8192 packet size: 1048576 time(ms): 25412 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 65536 packet size: 1048576 time(ms): 20322 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 1024 packet size: 262144 time(ms): 19048 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 8192 packet size: 262144 time(ms): 19227 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 65536 packet size: 262144 time(ms): 15141 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 1024 packet size: 65536 time(ms): 14983 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 8192 packet size: 65536 time(ms): 14801 fileSize:1073741824 block size:67108864 bufferSize: 4096 bpc: 65536 packet size: 65536 ... >From these results I can see performance declined with packet size increases. bpc didn't affect much though. >From my understanding, I think if I use less packets then I introduces less overhead and less read/write roundtrip. I couldn't explain what happened here. Can anyone give me some idea here?